The overlap rule turns edge rows and columns into free information. Start there and the middle of the board solves itself.
A Nonogram looks like it should be solved left to right, but the free information is almost never there. It is in the rows and columns whose clues nearly fill the available space.
Learn to spot those lines and the board opens up fast.
Find the lines that are nearly full
If a row of ten has a clue of 8, then at least six cells in that row are certainly filled regardless of where the block sits. Mark them and move on.
The overlap rule generalises: slide the block to each extreme and fill the intersection. It costs one mental step and returns free cells.
Work the edges before the middle
Edge rows and columns have fewer possible placements, so their overlaps are larger. The middle of the board usually has to wait for constraints from both directions.
A board solved edges-first tends to cascade: each completed edge line constrains the perpendicular lines crossing it.
Mark empty cells as aggressively as filled ones
Beginners only mark the cells they know are filled. Marking cells you know are empty is equally valuable, and it is usually what breaks a stalled board.
If a block cannot possibly reach a cell, cross it out immediately rather than leaving it ambiguous.